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add [manual_find
] lint for function return case
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Original file line number | Diff line number | Diff line change |
---|---|---|
@@ -0,0 +1,158 @@ | ||
use super::utils::make_iterator_snippet; | ||
use super::MANUAL_FIND; | ||
use clippy_utils::{ | ||
diagnostics::span_lint_and_then, higher, is_lang_ctor, path_res, peel_blocks_with_stmt, | ||
source::snippet_with_applicability, ty::implements_trait, | ||
}; | ||
use if_chain::if_chain; | ||
use rustc_errors::Applicability; | ||
use rustc_hir::{ | ||
def::Res, lang_items::LangItem, BindingAnnotation, Block, Expr, ExprKind, HirId, Node, Pat, PatKind, Stmt, StmtKind, | ||
}; | ||
use rustc_lint::LateContext; | ||
use rustc_span::source_map::Span; | ||
|
||
pub(super) fn check<'tcx>( | ||
cx: &LateContext<'tcx>, | ||
pat: &'tcx Pat<'_>, | ||
arg: &'tcx Expr<'_>, | ||
body: &'tcx Expr<'_>, | ||
span: Span, | ||
expr: &'tcx Expr<'_>, | ||
) { | ||
let inner_expr = peel_blocks_with_stmt(body); | ||
// Check for the specific case that the result is returned and optimize suggestion for that (more | ||
// cases can be added later) | ||
if_chain! { | ||
if let Some(higher::If { cond, then, r#else: None, }) = higher::If::hir(inner_expr); | ||
if let Some(binding_id) = get_binding(pat); | ||
if let ExprKind::Block(block, _) = then.kind; | ||
if let [stmt] = block.stmts; | ||
if let StmtKind::Semi(semi) = stmt.kind; | ||
if let ExprKind::Ret(Some(ret_value)) = semi.kind; | ||
if let ExprKind::Call(Expr { kind: ExprKind::Path(ctor), .. }, [inner_ret]) = ret_value.kind; | ||
if is_lang_ctor(cx, ctor, LangItem::OptionSome); | ||
if path_res(cx, inner_ret) == Res::Local(binding_id); | ||
if let Some((last_stmt, last_ret)) = last_stmt_and_ret(cx, expr); | ||
then { | ||
let mut applicability = Applicability::MachineApplicable; | ||
let mut snippet = make_iterator_snippet(cx, arg, &mut applicability); | ||
// Checks if `pat` is a single reference to a binding (`&x`) | ||
let is_ref_to_binding = | ||
matches!(pat.kind, PatKind::Ref(inner, _) if matches!(inner.kind, PatKind::Binding(..))); | ||
// If `pat` is not a binding or a reference to a binding (`x` or `&x`) | ||
// we need to map it to the binding returned by the function (i.e. `.map(|(x, _)| x)`) | ||
if !(matches!(pat.kind, PatKind::Binding(..)) || is_ref_to_binding) { | ||
snippet.push_str( | ||
&format!( | ||
".map(|{}| {})", | ||
snippet_with_applicability(cx, pat.span, "..", &mut applicability), | ||
snippet_with_applicability(cx, inner_ret.span, "..", &mut applicability), | ||
)[..], | ||
); | ||
} | ||
let ty = cx.typeck_results().expr_ty(inner_ret); | ||
if cx.tcx.lang_items().copy_trait().map_or(false, |id| implements_trait(cx, ty, id, &[])) { | ||
snippet.push_str( | ||
&format!( | ||
".find(|{}{}| {})", | ||
"&".repeat(1 + usize::from(is_ref_to_binding)), | ||
snippet_with_applicability(cx, inner_ret.span, "..", &mut applicability), | ||
snippet_with_applicability(cx, cond.span, "..", &mut applicability), | ||
)[..], | ||
); | ||
if is_ref_to_binding { | ||
snippet.push_str(".copied()"); | ||
} | ||
} else { | ||
applicability = Applicability::MaybeIncorrect; | ||
snippet.push_str( | ||
&format!( | ||
".find(|{}| {})", | ||
snippet_with_applicability(cx, inner_ret.span, "..", &mut applicability), | ||
snippet_with_applicability(cx, cond.span, "..", &mut applicability), | ||
)[..], | ||
); | ||
} | ||
// Extends to `last_stmt` to include semicolon in case of `return None;` | ||
let lint_span = span.to(last_stmt.span).to(last_ret.span); | ||
span_lint_and_then( | ||
cx, | ||
MANUAL_FIND, | ||
lint_span, | ||
"manual implementation of `Iterator::find`", | ||
|diag| { | ||
if applicability == Applicability::MaybeIncorrect { | ||
diag.note("you may need to dereference some variables"); | ||
} | ||
diag.span_suggestion( | ||
lint_span, | ||
"replace with an iterator", | ||
snippet, | ||
applicability, | ||
); | ||
}, | ||
); | ||
} | ||
} | ||
} | ||
|
||
fn get_binding(pat: &Pat<'_>) -> Option<HirId> { | ||
let mut hir_id = None; | ||
let mut count = 0; | ||
pat.each_binding(|annotation, id, _, _| { | ||
count += 1; | ||
if count > 1 { | ||
hir_id = None; | ||
return; | ||
} | ||
if let BindingAnnotation::Unannotated = annotation { | ||
hir_id = Some(id); | ||
} | ||
}); | ||
hir_id | ||
} | ||
|
||
// Returns the last statement and last return if function fits format for lint | ||
fn last_stmt_and_ret<'tcx>( | ||
cx: &LateContext<'tcx>, | ||
expr: &'tcx Expr<'_>, | ||
) -> Option<(&'tcx Stmt<'tcx>, &'tcx Expr<'tcx>)> { | ||
// Returns last non-return statement and the last return | ||
fn extract<'tcx>(block: &Block<'tcx>) -> Option<(&'tcx Stmt<'tcx>, &'tcx Expr<'tcx>)> { | ||
if let [.., last_stmt] = block.stmts { | ||
if let Some(ret) = block.expr { | ||
return Some((last_stmt, ret)); | ||
} | ||
if_chain! { | ||
if let [.., snd_last, _] = block.stmts; | ||
if let StmtKind::Semi(last_expr) = last_stmt.kind; | ||
if let ExprKind::Ret(Some(ret)) = last_expr.kind; | ||
then { | ||
return Some((snd_last, ret)); | ||
} | ||
} | ||
} | ||
None | ||
} | ||
let mut parent_iter = cx.tcx.hir().parent_iter(expr.hir_id); | ||
if_chain! { | ||
// This should be the loop | ||
if let Some((node_hir, Node::Stmt(..))) = parent_iter.next(); | ||
// This should be the funciton body | ||
if let Some((_, Node::Block(block))) = parent_iter.next(); | ||
if let Some((last_stmt, last_ret)) = extract(block); | ||
if last_stmt.hir_id == node_hir; | ||
if let ExprKind::Path(path) = &last_ret.kind; | ||
if is_lang_ctor(cx, path, LangItem::OptionNone); | ||
if let Some((_, Node::Expr(_block))) = parent_iter.next(); | ||
// This includes the function header | ||
if let Some((_, func)) = parent_iter.next(); | ||
if func.fn_kind().is_some(); | ||
then { | ||
Some((block.stmts.last().unwrap(), last_ret)) | ||
} else { | ||
None | ||
} | ||
} | ||
} |
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Original file line number | Diff line number | Diff line change |
---|---|---|
@@ -0,0 +1,22 @@ | ||
#![allow(unused)] | ||
#![warn(clippy::manual_find)] | ||
|
||
fn vec_string(strings: Vec<String>) -> Option<String> { | ||
for s in strings { | ||
if s == String::new() { | ||
return Some(s); | ||
} | ||
} | ||
None | ||
} | ||
|
||
fn tuple(arr: Vec<(String, i32)>) -> Option<String> { | ||
for (s, _) in arr { | ||
if s == String::new() { | ||
return Some(s); | ||
} | ||
} | ||
None | ||
} | ||
|
||
fn main() {} |
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Original file line number | Diff line number | Diff line change |
---|---|---|
@@ -0,0 +1,29 @@ | ||
error: manual implementation of `Iterator::find` | ||
--> $DIR/manual_find.rs:5:5 | ||
| | ||
LL | / for s in strings { | ||
LL | | if s == String::new() { | ||
LL | | return Some(s); | ||
LL | | } | ||
LL | | } | ||
LL | | None | ||
| |________^ help: replace with an iterator: `strings.into_iter().find(|s| s == String::new())` | ||
| | ||
= note: `-D clippy::manual-find` implied by `-D warnings` | ||
= note: you may need to dereference some variables | ||
|
||
error: manual implementation of `Iterator::find` | ||
--> $DIR/manual_find.rs:14:5 | ||
| | ||
LL | / for (s, _) in arr { | ||
LL | | if s == String::new() { | ||
LL | | return Some(s); | ||
LL | | } | ||
LL | | } | ||
LL | | None | ||
| |________^ help: replace with an iterator: `arr.into_iter().map(|(s, _)| s).find(|s| s == String::new())` | ||
| | ||
= note: you may need to dereference some variables | ||
|
||
error: aborting due to 2 previous errors | ||
|
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Why can't you do this in the
find(|(x, _)| ...)
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If we did that, the function would return the tuple instead of just the
x
. In the imperative version, the code would look something likeso it only returns the
x
and ignores the rest of the pattern, but in afind
the elements in the iterator remain as the entire tuple.